There are two things here. First, the sack of Constantinople, which for whatever reasons, was a horror afflicted on the Christians of the East by Christians of the West. It is true that the Ottoman Turks sacked Constantinople and raped, pillaged and murdered for three days, as was the custom in those days (the same length of time as the Fourth Crusade), but the Turks were not fellow Christians and they did not set up a Latin Patriarchate but actually elevated the Patriarch of Constantinople to be the Etnarch of all Christians (but the Armenians) in their empire. So, you have fratricide in a sense, combined with horrific crimes and this sort of thing understandably tends to affect folks.
At least Pope Innocent III thought so: "How, indeed, will the church of the Greeks, no matter how severely she is beset with afflictions and persecutions, return into ecclesiastical union and to a devotion for the Apostolic See, when she has seen in the Latins only an example of perdition and the works of darkness, so that she now, and with reason, detests the Latins more than dogs? As for those who were supposed to be seeking the ends of Jesus Christ, not their own ends, who made their swords, which they were supposed to use against the pagans, drip with Christian blood, they have spared neither religion, nor age, nor sex. They have committed incest, adultery, and fornication before the eyes of men. They have exposed both matrons and virgins, even those dedicated to God, to the sordid lusts of boys. Not satisfied with breaking open the imperial treasury and plundering the goods of princes and lesser men, they also laid their hands on the treasures of the churches and, what is more serious, on their very possessions. They have even ripped silver plates from the altars and have hacked them to pieces among themselves. They violated the holy places and have carried off crosses and relics." It should be noted however that when the crusaders took the piles of money, jewels, and gold that they had captured in the sack of Constantinople back to Rome, Innocent III welcomed the stolen items and agreed to let the crusaders back into the Church.http://en.wikipedia.org/wiki/Fourth_Crusade#Outcome
The second thing is that we must try to forgive this horror that occurred so many centuries ago. And, I think most Orthodox do not blame the current Roman Catholic Pope, bishops, priests or laity for this seminal event. What I think lingers on is the sense that the main problem with the West has been--before and after the Fourth Crusade--her claim of superiority and even primacy if you will. That is why the Fourth Crusade, the filioque clause, the added dogmas and divergent practices are all lumped together and viewed from the prism of the Papacy itself, which represents everything that has been and is wrong with the Roman Catholic Church.